[extropy-chat] ascii conversion of images?

[Johnius]

  I hope this isn't too off-topic for this list,
but I'm looking for an excellent ordered set of 
ascii characters to use in converting and 'shading'
satellite imagery into text pseudo-images.
  My current set is: ' ', '.', ',', ':', '-', '+',
'*', '&', '%', '#', going from light to dark.

  My boss will be on a ship for the next month
and he'll be able to get email, but not web access.
It's not clear if he'll be able to view or receive
as attachments jpeg(or other) images.
  He was going to have me simply describe the imagery
results verbally, but I think that good ascii-pictures
would be much better.
  I'm on an SGI workstation running IRIX 6.5 and have
been using IDL to do the conversion (example below).
  Does anyone have a great, well-tested set of ascii
characters to use in creating shading effects?
My current set has only 10 shading levels, and I suspect
that better selections exist.

  Another problem is that this method only works well
if the receiving system uses fixed-length fonts (i.e.,
each character is given a same-size spatial box to be
drawn in).  Systems with variable-length fonts will
"compress" vertically-thin characters and screw up
the 2-d spatial alignment of the pseudo-image.  One
way around this might be to select a set of ordered
characters that not only provide the shading illusion,
but also happen to have (nearly) the same widths.  This
second set might not be as optimized for shading effect,
but at least it would largely preserve the spatial 
relationships.

  Any suggestions/ideas?

  Here is a test image that I want to convert:
http://genius.ucsd.edu/~john/Lydwine_dir/S2002323195946_taua_865_m01_.03.jpg

  And here is my current best conversion, arbitrarily
set to 60 characters wide:

-:-%%++*. .,*LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
---%#**-...-*#LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
*-+%*++-..,:*%LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
+-++**+:..:-+*#LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
*+****+:.,--+-#LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
-+****+:.&---+&CLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
-+**+*+:,&--:*%+CLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
*&#%*&*:,+--:+--CLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
++*+*&-::+--:+::CLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
++#%%&-:-+-::+::-LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
&+%*&&-:-+::+-:::LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
&***&*+:-+-:+-:.:LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
&*%*&&+:+--,+-,.,LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
&+%&%%--+-+-*:...*LLLLLCLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
*+%#*&*-+--++-...,C:*---+LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
&&%#&*+--::+*-..  ,,,,:,*CLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
&&&%#*-+:--%*-.  ...,...+#CLLLCLLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
%+%##+-&-:-&*+.  ......,%#+&*##LLLLLLLLLLLLLLLLLLLLLLLLLLLLL                   
%%####---:-+*--.. :...LL:-:-++*#LLLLLLLLLLLLLLLLLLLCCLLLLLLL                   
%&&%#++-::-**:.  .,CLL&*-:.,::*CLCLLLLLLLLLLLLLLLLLL CLLLLLL                   
%*#*%&+::--&&:.. .,-#,,:,,  .,+:*%#CLLLLLLLLLLLLLLLLL C LLLL                   
###%%+--*+**+:,...,:,.,,.....::-:++#CLLLLLLLLLLLLLLLLL- LLLL                   
####*+-::-+#%:....,,,.,,,,.:-::-:-+###CLLLLLLLLLLLLLLLLCLLLL                   
%##%++--:-+%:,,...,,,,,-,,,:::,LL-+%%#+CLLLLLLLLLLLLLLLLLLLL                   
%###%+--:-*+,:,...,,:,,,,,,::::-LC*%*+*+CLLLLLLLLLLLLLLLLLLL                   
####*+----+--,,,..,:,,,:,,:-:::+-*-++---+LLLLLLLLLLLLLLLLLLL                   
###*++----*+-:,,.,,,:,,::::-:::-:+-:--,:-CLLLLLLLLLLLLLLLLLL                   
##&%*+---*%++,..,:::::::,L,-,,,:::::::-::*LLLLLLLLLLLLLLLLLL                   
####&+-+++*+-,,:,:,,,-:::+:::,,C.::,:::,,:LLLLLLLLLLLLLLLLLL                   
####&*-+*%+--,:::,.,-:::::--:,+:L,,,,::,.:CLLLLLLLLLLLLLLLLL                   
###&%%+++++&-,::,:.:--:,,,:-:+::CL.,:-:...CLLLLLLLLLLLLLLLLL                   
####%**+*+-*:,::::.,+-:,,,:::+:::,,,::, ..,-LLLLLLLLLLLLLLLL                   
####&&+++%++-:,,,,,,---::,:::,:,,,,,-:, ..-+LLLLLLLLLLLLLLLL                   
####**&%##+*--:,:,..,::+*,:,::,:,,,:,:. .,:#CLLLLLLLLLLLLLLL                   
####&****+*+--::-,,,,:,-:,,,...,::::,-...-*##LLLLLLLLLLLLLLL                   
#####*&+***++-:-:,,,...,:,,,:,.,:,:::...,:###&CLLLLLLLLLLLLL                   
#####******++---:,,,,...:,.,:,.,,,::,: .,,&##%-LLLLLLLLLLLLL                   
#####&#**&*%+---:::,:,..,,,.,,,::,::,...,:&#&%-LLLLLLLLLLLLL                   
######&#&++++-%-*:::,,,..,,,,:,::-,,....,,:&*+:&CLLLLLLLLLLL                   
#######%#&*&&+%-&::+,,,..,,,,-,*:-:,....,-,:::,-+CLLLLLLLLLL                   
###%#####%&+-&*---:::.,..,,,,::::-:...,,,-,:::,,:-LLLLLLLLLL                   
########%%&&+%&*--:::,.,.,,.,.:::::.,,:,:.,,,,.,:&LLLLLLLLLL                   
#########&****%*-::::,.,,:,,,,:--+:::,,:,  .....,:LLLLLLLLLL                   
#########*##*+*+--:,,,,:,:,,,,,-*+--::,,.,. .   ,+LLLLLLLLLL                   
############&%%+-::-+:,:--,,:,,+-++-:,,..,.     .,-%LLLLLLLL                   
#########&#***#&-:--:::,,,,:::,,-+-:::,:.,.    . ,,:CLLLLLLL                   
####%&#%&%##*###+*-:-:,,,,::--:,-+--:::,.,.   . ...,-*LLLLLL                   
############**##*--:,::,,::::-::-+&-::,:.... .... ,,:+LLLLLL                   
################+:-:-,::::,:-:-:-++-:::,.., ... ...,-+CLLLLL                   
C####%%#%#####%+----:::::::::-::--+-:::,.:,.......,*:-CLLLLL                   
C####%######*&%+-:-:::::,::-:-+:-++-:-::--,,,,,.,.,,::+#LLLL                   
CC###%#&*&####&----:::::,,-:::-+-++----:,:,,,,,,,,.:::++&CLL                   
C######&#&%#%+&-------:::,--::+*+*+*+-----:,,,,.,..::-+#:*LL                   
C######%&%%+#%---&--+-,,::--:++-&#&&+-:---:,,,,:,,.::-*#:*LL                   
########&%%+++&-+--++::,:,-+-+**+&&*+----::::-:--::::+%#-:CL                   
#######&&#&++++---++::::::---+#+##%*++::--::::-+++++%%##&&#C                   
######CC#&#&&**---::::,,:,-+-**&###&&+----::::-***#CCCCCCC.&                   
######CCCC#&%-+%-:::::::,::++-&%%#%***+------+-*+#CCCCCCCC#*                   
#CCCCCCCCC###*+++::::::::::&+**%##&&&++++++--+:-+%CCCCCCCC*C                   
#CCCCCCCCCCC#C#--:+::+::-::---+&##&&&++&++++*+++,CCCCCCCC-CC                   
CCCCCCCCCC###C#+---:*-::-::---+&*&&*#++*++++++*%CCCCCCCCCCC:                   
CCCCCCCCCC#CC###+-----::-:-:-+**&&&**%**++++***CCCCCCCCC#C-:                   
CCCCCCCCCC#CC###%-*-*--::++::-++-++++****+++*##CCCC#CCCCC+--                   
CCCCCCCCCCCCCC###+------:::-::--+-++*&&*#+*+&&CCCC#CCCC#*--:                   
CCCCCCCCCCCCCCC###-*--:-+*+------++**%*&****&%CCC##CCCC&+---                   
CCCCCCCCCCCCCCCCC#&++---:-*-*++--*&*&&&%&&**&CCCCC#CCC+&##--                   
CCCCCCCCCCCCCC####*:------++++#++**&**&&#%&%##CCCC#%%C%+CC--                   
CCCCCCCCCCCCCCCC#%C##--+:-****++&****+&###%%##CCCC&&CC&+*#+*                   
CCCCCCCCCCCCCCC####+##CC#:**&%&*&&#&***&######CCC-%&C*#+##CC                   
CCCCCCCCCCCC##C###-##*CCC###&&*#&*#&***&&*#%####CCCCCCCCCC#*                   
CCCCCCCCCCCCC###%#-%%+&######&#&&*******&&%#####%C-CCCC#CCCC                   
CCCCCCCCCCCCCC##&&**+#C#%###%****#++**&&&######**#*CC&CC+C.-                   
CCCCCCCCCCCCCC##C&&+*&CCCCC+%#*+***+&#*%*#%####***&#&%CC+#++                   
CCCCCCCCCCCCCCCCC##%#C#CCCCC#%#*#####:+*#C###C:++****&&&+C+-                   
CCCCCCCCCCCCCCCCCC#CCCCCCCCCC#&+*-++###*C ###C#%-++**++++*++                   
 
Southern California Current, 2002, day 323
Aerosol optical thickness, 865 nm
Total data range:       0.00000  to     0.327000
 
Legend
------
L = land
C = cloud
  ___   0.00000 or less
. ___   0.00177778
, ___   0.00355556
: ___   0.00533333
- ___   0.00711111
+ ___   0.00888889
* ___   0.0106667
& ___   0.0124444
% ___   0.0142222
# ___   0.0160000 or more

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